Heat sealing apparatus for filter rods

ABSTRACT

The travelling filter plug rod is wrapped with a heat seal paper and a seam sealer secures the overlapping edges of the heat seal paper to itself to effect a seam seal. Thereafter, the wrapped filter plug rod is severed into individual filter assemblies and each filter assembly is pushed through a heat chamber which effects a heat sealing of the paper to the remaining periphery of the filter plug. The heat chamber cooperates with a pair of hold down wheels or spring biased plates which maintain the travelling filter rod within the passageway of the heat chamber. The plates also serve to control the ejection speed of the filter assemblies.

United States Patent [1 1 Vanhall 2 [451 July 23, 1974 HEAT SEALING APPARATUS FOR FILTER RODS Inventor: Floyd Vanhall, Durham, N.C.

Liggett & Myers Incorporated, New York, NY.

Filed: July 3, 1972 Appl. No.: 268,816

Assignee:

References Cited UNITED STATES PATENTS Sexstone et a1. 93/1 C X Hall 93/77 FT 1 3,575,766 4/1971 McArthur 93/77 FT Primary Examiner-Roy Lake Assistant ExaminerJames F. Coan Attorney, Agent, or Firm-Kenyon & Kenyon [57] ABSTRACT The travelling filter plug rod is wrapped with a heat seal paper and a seam sealer secures the overlapping edges of the heat seal paper to itself to effect a seam seal. Thereafter, the wrapped filter plug rod is severed into individual filter assemblies and each filter assembly is pushed through a heat chamber which effects a heat sealing of the paper to the remaining periphery of the filter plug. The heat chamber cooperates with a pair of hold down wheels or spring biased plates which maintain the travelling filter rod within the passageway of the heat chamber. The plates also serve to control the ejection speed of the filter assemblies.

18 Claims, 11 Drawing Figures PATENIEnJuL23|s14 -3324908 sum inf 3 1 HEAT SEALING APPARATUS FOR FILTER RODS This invention relates to a heat sealing apparatus for sealing a strip of paper to a filter rod and particularly for sealing mouthpiece paper to a filter rod.

' Heretofore, various machines have been known for manufacturing filters for cigarettes. Generally, these machines have been constructed to deposit one or more filter media on a continuously moving strip of paper and to wrap the strip about the filter media to form a tubular filter rod. In order to secure the paper strip about the filter media, the machines have been provided with suitable devices to overlap and secure the longitudinal edges of the paper strip into a longitudinal seam. In some instances, the machines have been used a seam sealer which deposits a thin strip or layer of adhesive on one of the longitudinal edges of the paper strip prior to or during overlapping of the edges and which presses the overlapped edges together to allow the adhesive to secure the edges together in the seam. However, as the paper as not usually been secured directly to the filter media, it has been possible for the filter media to slide out from the paper tube after a filter has been made. Also, there isa possibility that the filter media can be dislodged from the inside surface of the paper tube so as to leave a space through which tobacco smoke can pass without being filtered to any significant degree.

In order to overcome these above disadvantages, various types of heat sealable paper and sealing devices have been used to effect a bonding of the paper completely about the filter media. For example, it has been known to use a relatively heavy paper which is precoated on one side with a thermosetting adhesive. This paper is first heated under pressure while folded about a filter media to heat and soften the adhesive and then cooled to set the adhesive. However, if the heated paper is not cooled with a suitable cooling device, the longitudinal seam has a definite tendency to burst open. Further, the heat has generally been applied directly to the heavy paper only in the area of the longitudinal seam and has thus required conduction through the paper to the remaining parts to effect the softening of the thermosetting adhesive.

Other machines have also been known in which a filter composed of charcoal and a copolymer binder are disposed within a tube formed of a paper web which is coated with a heat sealable plastic substances such as polyethylene lnitially, the filter materials have been deposited onto the travelling paper web and the web thereafter formed into a tube in a rod forming device. Heat has then been applied to the rod to cause the plastic to assume a tacky condition and seal around the filter material. Thereafter, the heated rod has been passed through a cooling unit to cool the rod.

Generally, these known machines have been of complex construction in order to provide a suitable heating means to effect the various sealing operations. In addition, the machines have required cooling means in addition to the heating means in order to effect securement of the paper wrapped about the filter media. Also, the papers which have been used have been relatively heavy and have frequently acted as a barrier to a rapid conduction of heat.

Accordingly, it is an object of this invention to provide a simple means of securing a continuous strip of paper about a length of filter media.

It is another object of this invention to provide a means of effecting a complete peripheral sealing of paper to a filter media.

It is another object of this invention to provide a simple two step technique for effecting a complete seal of a continuous strip of paper about a filter media.

Briefly, the invention is directed to a heat sealing apparatus which is incorporated into a machine for making cigarette filter assemblies and is used in combination with a seam sealer to effect a complete peripheral sealing of a continuous strip of paper about a length of filter media.

The heat sealing apparatus is located on the machine at a station downstream of the seam sealer and includes a heat chamber which defines a heated passageway for passage of a continuous length of paper-wrapped filter media and a hold-down means positioned in alignment with the passageway for maintaining the paperwrapped filter media within the passage during movement therethrough. In'addition, the heat sealing apparatus includes a means for heating the heat chamber to a temperature sufficient to impart sufficient heat to the paper passing through the passageway to heat seal the paper to the filter media.

'The paper utilized by the invention is a relatively inexpensive heat sealable type of relatively light weight and of a thin thickness such as Ecusta 3009.

In use, the seam sealer acts to initially form a longitudinal seam of the overlapped edges of the paper in a known manner about a length of filter media while securing the seam to the filter media. Thereafter, the heat sealing apparatus effects a securement of the remainder of the paper to the remainder of the filter media within a relatively short time without the application of any significant pressure.

The heat chamber is provided with a heater to heat the chamber to a suitable temperature, for example, in a range of from 450 F to 525 F. In order to control the heat of the heat chamber, two thermostats are incorporated therein, one to signal a minimum temperature and the other to signal a maximum temperature. The minimum temperature thermostat serves to actuate the heater when a lowermost temperature is reached while'the maximum temperature thermostat is used to deactivate the heater when a maximum temperature is reached. The heat chamber is generally made of block form with a U-shaped passageway in the upper surface for passage of the paper-wrapped filter media.

In one embodiment, the hold-down means is constructed with a pair of press wheels which are disposed in alignment with the passageway in the heat chamber in order to maintain the travelling paper wrapped filter media therein. Each of these wheels is rotatably mounted in a suitable support which is pivotally disposed to allow for alignment of the press wheels relative to the passageway in the heat chamber. In addition, the support for the press wheels is itself secured on a pivotally mounted support arm so as to be adjustable in height relative to the heat chamber. The support arm is, in turn, pivotally secured on a mounting plate and is provided with a lifting handle so as to be lifted or moved away from the heat chamber to provide access to the passageway therein.

In another embodiment, the hold-down means is constructed with a pair of spring biased plates which are aligned with the passageway in the heat chamber. Each 3 plate is in the form of a pressure finger which extends downwardly towards the heat chamber and is curved at the lower end for frictionally sliding against the paperwrapped filter media passing .therethrough. In addition, each plate is adjustably mounted relative to the heat chamber to effect a greater or less frictional force on the passing paper-wrapped filter media to control the throw of the paper-wrapped filter media from the heat chamber. Also, the plates are mounted at a different elevation above the heat chamber from each other within a suitable support to allow for alignment of the plates relative to the heat chamber.

The sealing apparatus is disposed within the filter making machine at a point downstream of the seam sealer as well as downstream of a suitable knife assembly which serves to sever a continuous rod of paper wrapped filter media into sequential filter assemblies. In this way, the individual filter assemblies are pushed through the passageway in the heat chamber by the following assernblies and rod..

The filter making machine can be of generally conventional structure. For example,-the machine can be of the type in which a supply of filter media, such as tow is wrapped into a cylindrical rod in a continuous strip of non-heat sealable plug wrap paper. Such a machine also includes a means to sever the resultant filter plug rod into individually spaced apart filter plugs, a means to deposit these plugs in spaced relation onto a travelling strip of mouthpiece paper, a means to inject agranulated filter media, such as activated charcoal, into the spaces between adjacent filter plugs and a means to wrap the strip of the mouthpiece paper about the filter plugs and granulated filter media to form a filter rod which is thereafter severed into determined lengths.

In use, the seam sealer is positioned downstream of a charcoal injection station to heat seal the overlapping edges of the mouthpiece paper to themselves and to the filter plugs after the paper has been folded over in the usual manner. The heat sealing apparatus of the invention serves to seal the mouthpiece paper directly to the filter plugs in the peripheral area outside the seam which was previously sealed by the seam sealer.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a schematic view of a machine for making filter assemblies which utilizes a heat sealing apparatus according to the invention;

FIG. 3 illustrates a cross-sectional view of a section of the filter rod to an enlarged scale;

FIG. 4 illustrates a cross-sectional view taken on line 4-4 of FIG. 1 through a seam sealer of the machine;

FIG. 2 illustrates a view taken on line 22 of FIG.

FIG. 9 illustrates a plan view of the heat sealing apparatus of FIG. 7; l

FIG. 10 illustrates a side view of a hold-down means according to the invention utilizing spring biased plates; and

FIG. 11 illustrates a front view of the hold-down means of FIG. 10.

Referring to FIG. 1, the machine 10 for making filter assemblies 11 is of generally known construction and includes a conveyor system 12 for receiving a supply of fibrous filter media 13, such as tow, from a suitable source at one end, a tube 14 for gathering and forming the tow into a cylinder, and a supply means 15 for supplying a continuous strip of non-heat seal plug wrap paper 16 for enveloping the tow to form a plug rod 18. In addition, a suitable means is provided to fold the longitudinal edges of the plug wrap paper 16 about the tow cylinder and a seam sealer 17 is provided to overlap and seal the longitudinal edges of the plug wrap paper 16 to form a seam. The plug wrap paperl6 is of known material which includes a chemical sealing compound on the surface facing the tow 13 so as to seal the plug wrap paper 16 directly to the paper 16 is also of a suitable weight to retain the tow 13 in a substantially cylindrical shape without deformation. The seam sealer 17 for the plug wrap paper 16 is of known construction and need not be further described.

The, machine 10 also includes a double knife assembly 19 which serves to sever the plug rod 18 into sequential spaced apart plugs 20. Also, a conveyor system 21 is mounted downstream of the double knife assembly 19 to receive and convey the individual plugs 20 on a travelling web 22 of mouthpiece paper supplied from a supply means 23. The mouthpiece paper 22 is of heat sealable material such as Ecusta 3009 and is of relatively light weight and thin thickness. In these latter respects the mouthpiece paper 22 is of lighter weight and thinner thickness then the plug wrap paper 16. Because of this, heat can be rapidly distributed through the mouthpiece paper 22. As shown, the mouthpiece paper 22 is delivered from a supply means 23 in the form of a roll over. a plurality of suitable guide rolls 24 and positioned onto the conveyor 21 so as to convey the filter plugs 20 thereon under a granulated filter media dispensing apparatus 25 such as a charcoal wheel. The dispensing apparatus 25 is timed and constructed to deposit granulated filter media 26 into the spaces between the filter plugs 20 (see FIG. 2). In addition, a gamiture section (not shown) is provided in which the mouthpiece paper 22 is sequentially formed into a U shape to receive the granulated filter media and thereafter enveloped over the filter plugs 20 and granulated filter media 26 into a tube-like cylinder with overlapping edges 27 (see FIG. 4).

Referring to FIGS. 1 and 4, a seam sealer 28 of known construction is positioned downstream of the dispensing apparatus 25 to heat seal the overlapping edges 27 of the mouthpiece paper 22 to each other and the enveloped filter plugs 20.

Referring to FIG. 4, the seam sealer 28 includes a heater bar 29 which is mounted over the travelling assembly of mouthpiece paper 22 and filter media and applies heat to the mouthpiece paper 22 in the area of the overlapped edges 27 to effect a seam seal longitudinally of the assembly and to form a continuous filter rod 30 (see FIG. 3). As shown, the heater bar 26 is tow 13. The plug wrap rounded to form the mouthpiece paper 22 into a tube. Also, a suitable guide (not shown) is provided to shape the conveyor ribbon 31 into a rounded shape and acts as a back-up for the heater bar 29.

Referring to FIG. 1, thefilter rod is conveyed to a single knife cutter 32 which is timed to sever the filter rod 30 into equal lengths of filter assemblies 11 each made up of a multi-sectional construction. For example, each assembly 11 is sized to provide two filters. These filter assemblies 11 are then pushed by the sections 11 behind as well as by the rod 30 through a heat sealing apparatus 33 which affects a heat sealing of the mouthpiece paper 22 to the remainder of the peripheries of the filter plugs 20 within each filter assembly 11.

Referring to FIGS. 7, 8 and 9, the heat sealing apparatus 33 includes a heat chamber 34, for example, made of an aluminum block of rectangular crosssection, which defines a U-shaped passageway 35 for the passage of the filter assemblies 11. The passageway 35 issized to slideably contact a substantial portion of the periphery of the filter assembliesll, e.g. one half of the peripheries while confining the filter assemblies 11 substantially wholly therein as shown. In addition, a heating means 36 such as an electrically heated bar is disposed within the block 34 to heat the block 34 to a suitable temperature. Also, the block 34 has two thermostats 37, 38 mounted therein wherein one thermostat 37 serves to activate the heating bar 36 at a predetermined temperature, such as 450 F, while the second thermostat 38serves to deactivate the heater bar 36 at a predetermined temperature such as 525 F.

In addition, a hold-down means 39 cooperates with the passageway 35 in the block 34 to maintain the moving filter assemblies 11 therein during heating. This hold-down means 34 includes a mounting plate 40 which is fixedly secured to the machine 10, a support arm 41 which is pivotally mounted by a bolt 42 at one end to the mounting plate 40 and a pair of press wheels 43 which are rotatably mounted in a support 44 secured on the support arm 41. As shown, the shafts of the press wheels 43 are held against axial movement in the support 44 by suitable stop collars 55.

The support arm 41 is disposed to pivot from a substantially horizontal position to a vertical position as shown in dotted line in FIG. 8. To this end, a lifting handle 45 is secured as by screw threading to the support 44 in a suitable fashion to permit lifting of the support arm 41. This lifting handle 45 is made of a vertically mounted bar having a knob 46 at the end. In addition, the press wheels 43 are mounted for rotation by suitable bearings within the support 44 which, in turn,

is secured by a pair of bolts 47 to the support arm 41.

The support 44 is provided with an elongated slot 48 through which the bolts 47 pass so as to permit a slight pivoting of the support 44 relative to the support arm 41. In this way, the press wheels 43 can be pivoted relative to each other to provide for alignment with the passageway 35 in the heating block 34. Each press wheel 43 is also provided with holes 49 so as to dissipate the heat transferred thereto from the heating block 34.

Further, as shown in FIG. 8, an extension bar 50 is secured to the mounting plate 40 to the underside of the support arm 41 and cooperates with a threaded screw 51 in the bottom of the support arm 40 to act as a stop so as to position the support arm 41 and, thus, the press wheels 43 relative to the passageway 35 in the 6 heating block 34. As shown, the adjusting screw 51 is threaded through the arm 41 and held in place by a bolt 52. In addition, a stop pin 53 is fixedly mounted on the mounting plate 40 so as to limit rearward pivoting of the support arm 41. t

In operation, as the severed filter assemblies 11 are ejected from the cutter 32, each passes into the U- shaped passageway 35 of the heating block 34. Thereafter, during travel through the heated block 34, each assembly 11 receives heat from the side walls and base of the U-shaped passageway 35 to such a degree as to effect heat sealing of the mouthpiece pape 22 directly to the filter plugs 20 within the peripheral area outside of the overlapped edges 26 of the mouthpiece paper 22 (FIG. 5).

After passing from the heat sealing apparatus 33, the

, mediate section formed by the granulated filter media all of which are enveloped by the mouthpiece paper 22.

Alternatively, as shown in FIGS. 10 and 11 wherein like reference characters indicate like parts as above, the hold-down means 56 is provided with a pair of spring biased plates 57 in the form of pressure fingers mounted in suitable holders 58 which are, in turn, mounted in clamped fashion in slotted bars 59. The

bars 59 are secured, as by welding, to the support 44 at different elevations, and extend from the support 44 toward the heat chamber 34. The support 44, as shown, is fixedly mounted by bolts 47 to the support arm 41. A bolt 60 is threaded through the slotted ends of each bar 59 so as to clamp the ends of the bars 59 together over a holder 58.

As shown, the plates 56 are aligned with the passageway 35 in the heat chamber to frictionally engage the filter assemblies 11. Depending upon the mounting of the plates 57 in the bars 59, the frictional force on the filter assemblies, 1 1 can be made more or less to control the throw of the filter assemblies 11 from the heat chamber 34. That is, the filter assemblies 11 can be ejected a less or greater distance from the heat chamber 34.

The invention thus provides a simple two step technique insuring a complete peripheral seal of mouthpiece paper to the filter plugs so as to prevent any slippage of the filter plugs from the filter assembly formed.

In addition, the two step heat sealing operation is carried out in a simple manner with simple equipment in a relatively rapid manner while the filter assemblies are made on-stream.

Since the mouthpiece paper 22 is relatively thin, the heat sealing apparatus 33 can be of relatively small bulk. For example, the heating block 34 can be 9 inches in length. Also, the amount of heat and the time required to effect-the heat seal is such as to eliminate the need for a separate cooling apparatus for cooling the filter assemblies. Further, because the time during which the filter assemblies are heated is relatively short, there is no large heat concentration built up within the filter assemblies. For example, the output rate of the machine is about 500 filter assemblies per minute.

What is claimed is:

strip of heat scalable paper circumferentially about said fed filter media with an overlap of the longitudinal edges of said paper,'a seam sealer for initially sealing said edges of said paper to each other and to said filter media, heat sealing means downstream of said seam sealer for subsequently sealing said paper to said filter media throughout the periphery of said filter media peripherally outside said overlapped edges, said sealing means including a heat chamber defining a heated passageway for passage of the paper wrapped filter media therethrough, and means for heating said heat chamber to a temperature sufficient to heat seal said paper to said filter media, and a hold-down means positioned in alignment with said passageway of said heat chamber for maintaining the paper-wrapped filter media therein during movement through said passageway, said holddown means including a pair of rotatably mounted press wheels for rollablyengaging the paper-wrapped filter mediain said passageway.

i 2. In an apparatus as set forth in claim 1 wherein said sealing means further includes a first thermostat in said heat-chamber to activate said'heating means in response to a first predetermined temperature of said heat chamber and a second thermostat in said heat chamber to de-activate said heating means in response to a second predetermined temperature of said heat chamber." 1 I 3. mm apparatus as set forth in claim 2 wherein said is 525 F and said passage is 9 inches in length.

- 4. In an apparatus as set forth in claim 1 wherein said hold-down means is adjustably mounted relativeto said passageway.

5. In an apparatus asset forth in claim 1 wherein said pressure wheels are pivotally mounted with respect to each other.

6. In an apparatus as set forth in claim 1 wherein said passageway is of U-shaped cross-section. I

7. In an apparatus for making filters having means for feeding filter media; means for wrapping a continuous strip of heat sealable paper circumferentially about said fed'filter media with an overlap of the longitudinal edges of said paper, a seam sealer for initially sealing Said edges of said paper to each other and to said filter media, and heat sealing means downstream of said seam sealer for subsequently sealing said paper to said filter media throughout the periphery of said filter media peripherally outside said overlapped edges, said sealing means including a heat chamber defining a heated passageway for passage of the paper wrapped filter media therethrough, and means for heating said heat chamber to a temperature sufficient to heat seal said paper to said filter media, a hold down means positioned in alignment with said passageway of said heat chamber for maintaining the paper-wrapped filter media therein during movement through said passageway, said hold-down means including at least one spring biased plate extending towards said heat chamber for frictionally engaging the paper-wrapped filter media passing through said heat chamber.

8. In an apparatus as set forth in claim 7 comprising a pair of said spring biased plates, each said plate being mounted at a different elevation above said. heat chamber from the other.

' first temperature is 450 F and said second temperature 9. In an apparatus as setforth in claim 7 wherein said plate has a curved lower end facing said heat chamber to slide against the passing paper-wrapped filter media.

10. In an apparatus as set forth in claim 7 wherein said plate is adjustably mounted relative to said heat chamber to effect a greater or less frictional force on a passing paper-wrapped filter medium 'to control the throw thereof from said heat chamber.

- 11. A heat sealing apparatus for sealing paper to a fibrous filter media comprising a heat chamber defining a heated passageway for passage of a length of paper-wrapped filter media therethrough;

means for heating said heat chamber to a temperature to impart sufficient heat to the paper passing through said passageway to heat seal the paper to the filter media; and

means positioned in alignment with said passageway for maintaining the paper-wrapped filter media therein during movement through said passageway, said latter means including a pair of rotatably mounted press wheels for rollably engaging the paper-wrapped filter media. 1

12. A heat sealing apparatus as set forth in claim 11 further comprising a first thermostat in said heat chamber to activate said heating means in response to a first predetermined temperature of said heat chamber and a second thermostat in said heat chamber to' de-' activate saidheating means in response to a second predetermined temperature of said heat chamber.

13. A heat sealing apparatus as set forth in claim 11 wherein said press wheels are adjustably mounted with respect to said heat chamber and pivotally mounted with respect to each other. I I

14. A heat sealing apparatus as set forth in claim 11 wherein said means for maintaining the paper-wrapped filter media in said passageway is mounted for movement away from said heat chamber.

15. A heat sealing apparatus for sealing paper to a fibrous filter media comprising aheat chamber defining a heated passageway for passage of a length of paper-wrapped filter media therethrough; I

means for heating said heat chamber to a temperature to impart sufficient heat to the paper passing through said passageway to heat seal the paper to the filter media; and

means positioned in alignment with said passageway for maintaining the paper-wrapped filter media therein during movement through said passageway, said latter means including at least one spring biased plate extending towards said heat chamber for frictionally engaging the paper-wrapped filter media passing through said heat chamber.

16. A heat sealing apparatus as set forth in claim 15 comprising a pair of said spring biased plates, each said plate being mounted at a different elevation above said heat chamber from the other.

17. A heat sealing apparatus as set forth in claim 15 wherein said plate has a curved lower end facing said heat chamber to slide against the passing paperwrapped filter media.

18. A heat sealing apparatus as set forth in claim 15 wherein said plate is adjustably mounted relative to said heat chamber to effect a greater or less frictional force on a passing paper-wrapped filter media to control the throw thereof from said heat chamber. 

1. In an apparatus for making filters having means for feeding filter media; means for wrapping a continuous strip of heat sealable paper circumferentially about said fed filter media with an overlap of the longitudinal edges of said paper, a seam sealer for initially sealing said edges of said paper to each other and to said filter media, heat sealing means downstream of said seam sealer for subsequently sealing said paper to said filter media throughout the periphery of said filter media peripherally outside said overlapped edges, said sealing means including a heat chamber defining a heated passageway for passage of the paper wrapped filter media therethrough, and means for heating said heat chamber to a temperature sufficient to heat seal said paper to said filter media, and a hold-down means positioned in alignment with said passageway of said heat chamber for maintaining the paper-wrapped filter media therein during movement through said passageway, said hold-down means including a pair of rotatably mounted press wheels for rollably engaging the paper-wrapped filter media in said passageway.
 2. In an apparatus as set forth in claim 1 wherein said sealing means further includes a first thermostat in said heat chamber to activate said heating means in response to a first predetermined temperature of said heat chamber and a second thermostat in said heat chamber to de-activate said heating means in response to a second predetermined temperature of said heat chamber.
 3. In an apparatus as set forth in claim 2 wherein said first temperature is 450* F and said second temperature is 525* F and said passage is 9 inches in length.
 4. In an apparatus as set forth in claim 1 wherein said hold-down means is adjustably mounted relative to said passageway.
 5. In an apparatus as set forth in claim 1 wherein said pressure wheels are pivotally mounted with respect to each other.
 6. In an apparatus as set forth in claim 1 wherein said passageway is of U-shaped cross-section.
 7. In an apparatus for making filters having means for feeding filter media; means for wrapping a continuous strip of heat sealable paper circumferentially about said fed filter media with an overlap of the longitudinal edges of said paper, a seam sealer for initially sealing said edges of said paper to eAch other and to said filter media, and heat sealing means downstream of said seam sealer for subsequently sealing said paper to said filter media throughout the periphery of said filter media peripherally outside said overlapped edges, said sealing means including a heat chamber defining a heated passageway for passage of the paper wrapped filter media therethrough, and means for heating said heat chamber to a temperature sufficient to heat seal said paper to said filter media, a hold down means positioned in alignment with said passageway of said heat chamber for maintaining the paper-wrapped filter media therein during movement through said passageway, said hold-down means including at least one spring biased plate extending towards said heat chamber for frictionally engaging the paper-wrapped filter media passing through said heat chamber.
 8. In an apparatus as set forth in claim 7 comprising a pair of said spring biased plates, each said plate being mounted at a different elevation above said heat chamber from the other.
 9. In an apparatus as set forth in claim 7 wherein said plate has a curved lower end facing said heat chamber to slide against the passing paper-wrapped filter media.
 10. In an apparatus as set forth in claim 7 wherein said plate is adjustably mounted relative to said heat chamber to effect a greater or less frictional force on a passing paper-wrapped filter medium to control the throw thereof from said heat chamber.
 11. A heat sealing apparatus for sealing paper to a fibrous filter media comprising a heat chamber defining a heated passageway for passage of a length of paper-wrapped filter media therethrough; means for heating said heat chamber to a temperature to impart sufficient heat to the paper passing through said passageway to heat seal the paper to the filter media; and means positioned in alignment with said passageway for maintaining the paper-wrapped filter media therein during movement through said passageway, said latter means including a pair of rotatably mounted press wheels for rollably engaging the paper-wrapped filter media.
 12. A heat sealing apparatus as set forth in claim 11 further comprising a first thermostat in said heat chamber to activate said heating means in response to a first predetermined temperature of said heat chamber and a second thermostat in said heat chamber to de-activate said heating means in response to a second predetermined temperature of said heat chamber.
 13. A heat sealing apparatus as set forth in claim 11 wherein said press wheels are adjustably mounted with respect to said heat chamber and pivotally mounted with respect to each other.
 14. A heat sealing apparatus as set forth in claim 11 wherein said means for maintaining the paper-wrapped filter media in said passageway is mounted for movement away from said heat chamber.
 15. A heat sealing apparatus for sealing paper to a fibrous filter media comprising a heat chamber defining a heated passageway for passage of a length of paper-wrapped filter media therethrough; means for heating said heat chamber to a temperature to impart sufficient heat to the paper passing through said passageway to heat seal the paper to the filter media; and means positioned in alignment with said passageway for maintaining the paper-wrapped filter media therein during movement through said passageway, said latter means including at least one spring biased plate extending towards said heat chamber for frictionally engaging the paper-wrapped filter media passing through said heat chamber.
 16. A heat sealing apparatus as set forth in claim 15 comprising a pair of said spring biased plates, each said plate being mounted at a different elevation above said heat chamber from the other.
 17. A heat sealing apparatus as set forth in claim 15 wherein said plate has a curved lower end facing said heat chamber to slide against the passing paper-wrapped filter media.
 18. A heat sealing apparatus as set forth in claIm 15 wherein said plate is adjustably mounted relative to said heat chamber to effect a greater or less frictional force on a passing paper-wrapped filter media to control the throw thereof from said heat chamber. 